As for the thread starter, I bought my first bike in 09 and I looked at mostly personal listings. I don't recall seeing as much of those don't waste my time ads as I see these days. Of course, I didn't test ride any bikes at that time because I didn't have the experience nor a license at that point. I bought my first bike without ever having ridden. But I did check it out real well and I got a lot of advice on that particular model. I was going for a cruiser and a lot of people recommended a Honda Shadow 750 or a Yamaha VStar 650(?). I ended up with the Shadow.
Recently, I upgraded to a Harley. I test rode bikes at 2 dealerships and I'm pretty sure I could have test rode at the other 2 places, as well, if I chose to do that. The first place, Gail's Harley Davidson in Grandview made me fill out a form that basically said if I wrecked it, I buy it. The paperwork made it sound like they would require that I followed/rode with someone from their dealership. But when I got out there and asked about that, the salesman said they weren't planning to ride with me unless I wanted them to. Of course I declined and test rode a couple bikes by myself.
The other place, Topeka Harley let me ride without anything other than a copy of my license. Of course, they did know that I had a bike and was looking to sell it or trade it in to them.
I do wonder, however if its up to their discretion as to whether they allow you to test ride solo or whatever.